How to extend my wlan at home?

Hello Guys!

I live in a house with an garage outside, distance between the bulidings is like 20 meters.
In my house I got a small router, that provides my wlan. Anywhare inside my house I get a good connection.

But when I take my laptop outside to my garage, the connection is weak like 25%.

How do I fix this in the best way?
I have heard about "Access points". But if I buy and add one of these gadgets in my wlan, and put it inside my garage, how will it increase my connection when it is alraedy weak? Or should I put the new access point in between the buildings where the conncetion still is strong?

Hope you get it?

Best regards
Fredrik